Climate Change

Climate change involves natural and man-made changes to weather
patterns that occur over millions of years or over multiple
decades.

In the past 150 years, human industrial activity has accelerated
the rate of change in the climate due to the increase in
greenhouse gases (carbon dioxide, methane and nitrous oxide,
among others). Scientific studies describing this climate change
continue to be produced and its expected impacts continue to be
assessed.

The report’s 36 indicators were grouped as human-influenced
drivers of climate change, such as greenhouse gas emissions;
changes in the state’s climate; impacts of climate change on the
Pacific Ocean, lakes and snowpack; and impacts of climate change
on people, vegetation and wildlife.

The report pointed to the devastating 2017 wildfires across the
state and the record-setting 2012-2016 drought as examples of the
types of climate change-related challenges that will confront
California in the future.

Already, California is confronting rising demand for water and
diminishing supplies. At the same time, the state’s water
infrastructure such as levees is aging and in
disrepair—conditions expected to be made worse by climate change.

Expected Impacts in California

Facts and figures for the potential impact of climate change
continue to be unveiled. Recent reports by the California
Environmental Protection Agency, California Energy Commission and
California Natural Resources Agency have concluded:

Precipitation patterns are changing, with more rain, less
snow and shrinking glaciers in the Sierra Nevada (the primary source
of much of California’s fresh water supplies)

Less snowpack and earlier springtime melting are reducing
hydropower capacity

Rising sea levels will also worsen coastal flooding
and push more salty ocean water into coastal groundwater
aquifers and possibly swamp key infrastructure such as airports
and ports

Hotter temperatures will also lead to more wildfires of
increased intensity; already more than half of California’s
largest wildfires have been in the last decade

Dry weather will lead to more tree deaths and altered
vegetation patterns, with some plants moving to higher ground

More wildlife is also expected to change habitat, with some
already migrating to higher ground

Hotter weather also will likely lead to more potentially
lethal heat waves and related water shortages and droughts

Oceans and lakes are likely to see their average water
temperatures rise (Lake Tahoe
has risen by nearly 1 degree in the past three decades)

Cold periods in winter needed for growing fruits and nuts
will be shorter

Native freshwater fish are particularly vulnerable to climate
change and a 2013 University of California, Davis study found 82
percent of California native fish species are at risk of
extinction

In a 2017 report, Anthropogenic Warming Impacts on California Snowpack During
Drought, researchers with the Department of
Atmospheric and Oceanic Sciences at University of California,
Los Angeles, found that anthropogenic warming reduced average
snowpack levels by 25 percent and that under a severe drought
scenario, “further snowpack declines of 60 percent to 85
percent are expected, depending on emissions scenario.”

Responding to Climate Change

The focus on climate change has prompted many in the water
community to call for a comprehensive response on the part of
state, federal and local officials.

Many water agencies are already including climate change impacts
in their long-term planning, factoring in a need for increased
conservation, groundwater banking, water recycling and new
surface storage projects. Also under consideration by some water
districts and agencies is seawater desalination.

In 2006, then California Gov. Arnold Schwarzenegger signed into
law Assembly Bill 32, making the state the first in the nation to
impose a cap on all greenhouse gas emissions. The law aims to
reduce the state’s emissions of carbon dioxide and other
greenhouse gases by an estimated 25 percent by 2020.

In 2016, then-Gov. Jerry Brown signed
legislation that requires California’s emissions
to fall to 40 percent below 1990 levels by 2030. Brown followed
that up in 2017 by signing legislation to extend AB 32,
which requires oil refineries, power plants, food processors
and other facilities to purchase permits to release carbon
dioxide into the atmosphere.

In 2019, Gov. Gavin Newsom signed an executive order directing
his administration to develop a comprehensive strategy to build a
climate-resilient water system. In 2020, he proposed a five-year,
$12 billion climate budget including a Climate Catalyst Fund to
invest in small businesses and emerging markets for new
technologies that would help California reduce its greenhouse gas
emissions.

Still, some are skeptical of proposals to limit emissions of
greenhouse gases and the potential economic impacts of such
actions. Political debate has centered on the merits of the
science used to justify various claims. Meanwhile, some in the
business community say efforts to enact greenhouse gas emission
reductions in California through arbitrary means are
counterproductive, given the scale of global emissions and the
fact that companies could move their operations to places without
emissions caps.

While the state works to balance the needs of multiple interests,
climate change and population growth pose additional future
challenges.

The state’s population of about 40 million in 2019 was
expected to reach 43.4 million by 2036, according to the
California
Department of Finance. Climate change adds complexities and
questions to this growth and related environmental impacts in the
future.

These remain key issues as state experts work to determine how to
best incorporate a changing climate into water management
planning, including flood planning due to a sea level rise, peak
flow changes and a reduced snow pack.

Related Links

Evidence shows that climate change is affecting California with
warmer temperatures, less snowfall and more extreme weather
events. This guide explains the causes of climate change, the
effects on water resources and efforts underway to better adapt
to a changing climate. It includes information on both California
water and the water of the Colorado River Basin, a widely shared
resource throughout the Southwest.